Disk Masses for Embedded Class I Protostars in the Taurus Molecular Cloud

Abstract

Class I protostars are thought to represent an early stage in the lifetime of protoplanetary disks, when they are still embedded in their natal envelope. Here we measure the disk masses of 10 Class I protostars in the Taurus Molecular Cloud to constrain the initial mass budget for forming planets in disks. We use radiative transfer modeling to produce synthetic protostar observations and fit the models to a multi-wavelength data set using a Markov Chain Monte Carlo fitting procedure. We fit these models simultaneously to our new Combined Array for Research in Millimeter-wave Astronomy 1.3 mm observations that are sensitive to the wide range of spatial scales that are expected from protostellar disks and envelopes so as to be able to distinguish each component, as well as broadband spectral energy distributions compiled from the literature. We find a median disk mass of  M 0.018 on average, more massive than the Taurus Class II disks, which have median disk mass of~ M 0.0025 . This decrease in disk mass can be explained if dust grains have grown by a factor of 75 in grain size, indicating that by the Class II stage, at a few Myr, a significant amount of dust grain processing has occurred. However, there is evidence that significant dust processing has occurred even during the Class I stage, so it is likely that the initial mass budget is higher than the value quoted here.

From grains to pebbles: the influence of size distribution and chemical composition on dust emission properties

“…Denser and more evolved regions exhibit much shallower dust SEDs in the FIR to millimetre wavelength range with spectral indices lower than in molecular clouds and even lower than in the diffuse ISM. This was observed in the first hydrostatic core candidates (Young et al 2018) and YSOs (Chiang et al 2012;Miettinen et al 2012;Miotello et al 2014;Choi et al 2017;Gerin et al 2017;Sheehan & Eisner 2017) with spectral index values below 1.5. Observations of protoplanetary discs also show very low spectral index values (e.g.…”

Formation and Evolution of Disks Around Young Stellar Objects

“…Similar measurements were found using a different analysis technique with lower-resolution data by Andersen et al (2019) and data at 1.3 mm, indicating that the measurements from Ophiuchus are very low compared to the Perseus region. Moreover, modeling of the Class I protostars in Taurus using CARMA data also finds larger Class I disk mass as compared to Ophiuchus (Sheehan and Eisner 2017). Thus, we can conclude that disk masses toward protostars are systematically larger than the more-evolved Class II disks, but it is unclear if the mean protostellar disk masses are similar between regions or if we should expect them to be similar, given the differences seen in the Class II populations with similar ages (Williams et al 2019;Cazzoletti et al 2019).…”

High-precision Dynamical Masses of Pre-main-sequence Stars with ALMA and Gaia

“…pdspy can handle both spectral line and continuum observations, and is now publicly available. The continuum portion of the code was used in Sheehan & Eisner (2017) but the code was not formally introduced at that time.…”